Key Terms Precipitation – any way that water

reaches the ground from the air e.g. rainfall, sleet and snow

Infiltration – the movement of water from the earths surface into the soil

Surface run off – the transfer of water back to the sea over the surface of the land.

Transpiration - Plants letting water out into the atmosphere as a vapour.

Groundwater - The transfer of water through the ground back to the sea.

Condensation - Water vapour in the air changing back as a liquid, creating clouds.Air

Land SeaKey Words

Drainage basin – the area of land drained by a river and its tributaries

Source – where a river starts, usually in the highlands

Mouth – where the river meets a lake or the sea

Watershed – the imaginary line that divides two drainage basins

Tributary – a smaller river that joins a main river

Confluence – the joining point of two rivers

The Hydrological Cycle

The hydrological cycle or water cycle is a CLOSE system. It is the continuous movement of water between land, sea and the air.

The Drainage Basin

The drainage basin in an open system – the amount of water in it is not fixed.

Processes of a river

ErosionThere are four ways that a river erodes; hydraulic action, corrosion, corrosion and attrition.

Hydraulic action – the force of the water wearing away the bed and bank of the river

Corrosion – the chemical reaction between the water and the bed and bank of the river, wearing it away.

Corrasion/abrasion – where bedload in the river wears away its bed and bank.

Water on the Land

Attrition – where rocks in the water become smaller and rounder by hitting each other.

TransportationThere are four ways in which a rivers moves its eroded material downstream; traction, saltation, suspension and solution.

DepositionThis is where the river drops its material. It occurs when the velocity of the

river decreases, energy is reduced and the river can no longer hold all its material.

Characteristics of the upper course of the river

Land use

Forestry

evergreen fern trees to cut down and sell

Hill sheep farming

Tourism e.g. white water rafting, hiking

Mountainous

Lowest velocity

a lot of friction along bed and bank

little water

Turbulent water

large, jagged, angular boulders

no erosion by attrition yet

too large to carry unless river in flood

steep gradient

water is very clear

Little erosion has taken place

vertical erosion dominant

waterfall and rapids

v-shape valley

Hydroelectric power Most transported material is bedload, little is in suspension

Characteristics of the upper course of the river

Features of the upper course

VERTICAL EROSION is the main process in the upper course of the river, as the river wants to get to sea level. This process creates five distinctive features; a v-shaped valley, interlocking spurs, waterfalls, gorges and rapids.

1. V-shaped valley

2. Interlocking spurs

a) b) c)

Vertical erosion

Weathering and soil creep

v-shaped valley

V-shaped valleys are created by vertical erosion (a). As the river erodes downwards freeze-thaw weathering loosens material, which is moved downhill by soil creep (gravity) (b). This creates the characteristic v-shaped valley only found in the upper course of the river. It is steep sided and narrow.

Interlocking Spurs are caused because the river wants to erode vertically. It therefore winds it way around areas of hard rock, avoiding them in favour of softer rock which is more easily eroded and leaves them as ridges of interlocking spurs.

3. Waterfalls

These occur when there are horizontal bands of hard and soft rock.

An example is High Force on the River Tees

4. Gorges

The Characteristics of the middle Course of the River

Gorges are the results of the waterfalls retreating upstream. As the process of undercutting and collapse repeats, the waterfall moves back towards its source. This leaves a steep sided channel called a Gorge. An example of this is Katherine Gorge, Australia.

Cross section of a Meander

Characteristics of the middle course

of the river

Land Use

Dairy and Arable farming

Settlements

Industry

Transport

Housing

Lateral erosion is the dominant process

Meanders

Ox-bow lakes

Meander scar

Floodplains

Meander migration

Smaller, smoother and rounder sediment transported in the river

Attrition has eroded material

Smaller material carried in suspension

River water less clear

Erosion of the banks and bed have increased suspended load

Hydraulic action

Corrosion Corrasion

River has greater energy

More suspended load

Gradient is much more gentle

Closer to sea level

Vertical erosion is reduced

Velocity is increased

tributaries adding water

Less friction Turbulence is reduced

Features of the middle course

LATERAL EROSION is the dominant process in the middle course of the river, as it is getting closer to sea level, so doesn’t want to erode downwards, but has more energy due to increased volume of water. Therefore the river erodes sideways. This process creates four distinctive features; meanders, oxbow lakes, floodplains and levees.1. Meanders

A meander is a bend in a river. On the outside of the bend the river is fastest flowing and therefore erosion is greatest. This creates a deep area of water and a river cliff. On the inside of the bend water is forced to slow down, which reduces its energy, making it deposit its material. This creates a shallow slip of slope.

2. Ox-bow lakes1. Erosion on the outside of the bend is caused by the fastest flowing water hitting it. This creates a river cliff. Deposition occurs on the inside of the bend due to the water being forced to slow down. This creates a slip off slope.

Diagram of Meander Migration

3. Floodplains

A floodplain is the wide, flat area of land either side of the river. It is formed by erosion and deposition. As meanders slowly move downstream, lateral erosion widens the floodplain, whilst deposition of the slip off slopes provides sediment to build up the floor. In addition, when the rivers floods sediment is deposited on the floodplain, making it very fertile. This makes it perfect for agriculture and is why many farmers are found on floodplains.

4. Levees

Levees are natural embankments that form by the banks of the river. They are created by deposition. When a river floods, the velocity of the river slows down as it travels over the floodplain. The river cannot hold all its sediment and is forced to deposit it. It deposits the largest material first and the smallest furthest from the river bank: this is called sorting. This process repeats over time creates a levee.

4. Deposition occurs on the outside of the channel, blocking up the former meander to create an ox-bow lake. Over time the ox-bow lake dries up to create a meander scar.Key//// = erosion::::::: = deposition = fastest flowing water

2. As erosion occurs on the outside of the bend, the meander neck narrows.

3. The meander neck gets so narrow that during a flood event the river cuts through, creating a new straight channel.

Characteristics of the lower course of the river

Characteristics of the lower course

of the river

Land Use

Dairy and Arable farming

Settlements

Industry

Transport

Housing

Lateral erosion is still dominant

Meanders

Ox-bow lakes

Meander scar

Floodplains

Meander migration

Smallest sediment transported in the river called alluvium

Attrition has eroded material

Smaller material carried in suspension

River water least clear

Erosion of the banks and bed have increased suspended load

Hydraulic action

Corrosion Corrasion

River has greatest energy

More suspended load

Flat gradient

At sea level

Vertical erosion is reduced

Velocity is greatest

tributaries adding water

Less frictionTurbulence is reduced

Import and exports

Mouth of the river

Deposition at the mouth

Energy reduced

Deltas Estuaries

Features of the lower course

The river has greatest discharge and cross-sectional area. Many of the characteristics are similar to the middle course, including the floodplain, levees and meanders. However, due to reduced velocity at the mouth of the river it also has one additional feature; deltas.

1. Deltas

Causes of flooding

Deltas form at the mouth of river. The velocity of the river is reduced, so it deposits its material. This begins to choke the mouth of the river, and so it splits into smaller channels called distributaries. There are three types of delta; fan, tooth and bird’s foot.

Key Words Discharge – the amount of water in a river channel measured in cumecs (m/sec³) Rising limb – this increase in river discharge, due to surface runoff Falling limb- the return to normal levels of river discharge after the storm event,

slowed by through flow. Lag time – the time between the heaviest rainfall and the highest discharge. The

shorter the lag time the greater the risk of flooding. Peak discharge – maximum volume of water in the river.

Causes of flooding

Surface run off in the key to flooding

Physical Causes Human Causes

deforestationurbanisation

global warming

sea level rise

snowmelt

reliefgradient

soil type

prolonged heavy rainfall

short intense rainfall

population density

vegetation

drainage basin shape

The Storm Hydrograph

A hydrograph is a graph which shows the discharge of a river over time, at a given point. A storm hydrograph shows the change in discharge during a storm event

The long profile of the river

Upper Course Middle course Lower courseLong Profile Steep gradient Gentle gradient flatValley cross

section

Channel cross section

Examples of features

V-shaped valley, waterfalls, rapids,

gorges

Meanders, ox-bow lakes, floodplain,

levee

Meanders, ox-bow lakes, levee, deltas

River Features on Maps

1. The upper course

2. The middle course

Contours slope down toward the river in a v-shape. This shows and interlocking spur.

Contours are close together, showing a steep sided valley.The contours continue right to the river showing there is no floodplain (flat land next to the river).

Meanders are evident in this part of the river.

Towns are often found in this section of the river.

Characteristics of the River Tees

Upper CourseLocation

North-east England

Source in the Pennines

Mouth in the North Sea

River flows from west to east

Middlesbrough

Cross Fell 893m above sea level

2000mm rainfall per year

Impermeable rock

High surface run off

Steep v-shape valley Steep

gradient

Turbulent, clear water

Many rapids

High Force waterfall

One of largest in England

Made up of Whinstone, with Sandstone below it

Gorge has formed

Middle Course

Meanders

YarmStockton

Meanders cut off in C19th for boats navigation

Bridging points

Lower Course

Large meander loops

Industry

Manufacturing

Imports Exports

Coal

Hill sheep farming

Large boulders

Farming

Smaller sediment

Smoother

Rounder

Teesmouth

Mud Flats

Alluvium

Smallest sediment

Wildlife

SealsMigratory birds

Shipping

Widest channel

3. The lower course

The River Tees

The drainage basin of the river Tees

The contour lines are much further spaced out – showing a much flatter gradient.

The land close to the river has no contours – showing a flat floodplain.

River is at its widest.

Deposition is evident, usually as mud flats or deltas.

Heavy industry is often found at the lower course.

The land has very few contours. It is very flat.

The Boscastle flood 2004

Causes Effects

Human

Physical Immediate

Secondary

Boscastle is at the confluence point of the Valency and Jordan rivers

The soil was saturated due to rainfall earlier in the week

Very heavy rainfall

185mm in 5 hours

Valleys are very steep sided

lots of surface run off

Rock type is shale and slate

ImpermeableHigh tide in the bay

Land use agriculture

little infiltration

The B3263

narrowed the river channel

reduced volume of the river

Bridge across the river

Acted as a dam

6 houses destroyed

£135,000 damage

1 heart attack (no deaths)

Witch Museum damaged

Both bridges destroyed

Telephone, water, electricity and gas supplies disrupted

Loss of tourism

Businesses flooded get compensatede

Knock on effects to businesses not flooded

Fall in house pricesTrauma caused by residents

The Bangladesh flood 2004

Causes Effects

Solutions

Human

Deforestion in Nepal Urbanisation

soil erosion

deposition in river channel

Farakka dam

reduced Hooghly river bed

living on the floodplain

impermeablesurface

Physical

Heavy monsoon rainfall

2000mm

Shape of the Bay of Bengal

increases coastal flooding

70% land is <1m above sea level

floodplain of the Ganges, Brahmaputra and Meghna

Snowmelt in the Himalayas

10% land is covered in rivers, lakes and swamps

Immediate

760 people killed

8.5 million people left homeless

Roads and bridges were damaged and destroyed

Floods covered over 50% of Bangladesh

Rice growing was disrupted

Fish farming was disrupted

Secondary 1 million+ children suffered malnutrition and disease

Rebuilding cost the government £1.5 billion

Emergency food aid was needed until the following year's harvest

Long term

Building flood shelters

cultural problems

Flood warning systems

education

posters

forecasting satellites

Building embankments

loud speakers

flags

Appropriate farming and fishing methods

Short term

World Bank Action Plan for Flood Control

Emergency aid

water purification tablets

boats for rescuing people

foodmedicine

plastic sheets

repairing homes

The Boscastle Flood, 16 th August 2004

The Bangladesh Flood,July-September 2004

Managing Floods

Responses: New culvert was

built Car park was

raised and barriers put around it

River was widened and deepened

Bridges made taller

Cost = £4.6 million

MEDC Case Study: River Derwent

£7.5 million has been spent on protecting towns in the catchment area. They have used hard and soft methods to protect against future flooding.

Hard Engineering scheme case study: Three Gorges Dam

The Three Gorges Dam is built on the Yangtze River. The Dam is 181m high and 2.3km long. Construction started in 1994 and finished in 2006 and cost $25.5 billion. A reservoir has been created by the dam which is 632km².

Hard engineering:

Embankments have been put along the river, these are now quite old and didn’t protect against the floods in 1999

Sluice gates upstream can hold back water and let it out in a controlled way.

The area is quite rural so expensive schemes are not worth the money for the whole area.

Flood gates have been put at Stamford Bridge to protect the road and homes

Flood walls at Stamford Bridge have been built to protect homes and businesses.

Soft Engineering:

Embankments have been built near settlements with washlands between the embankments and the river. Water can flood here without causing damage

New building has been restricted on the floodplain

Hedgerows and trees have been planted

River banks have been reinforced with willow to stop bank erosion so that the river doesn’t get silted up

Early warning systems have been put in place

Advantages Disadvantages Has provided flood control. The

risk of flooding downstream went from a 1-in-10 year event to a 1-in-100 year event.

The dam will benefit over 15 million people living in high-risk flood areas,

The dam will protect over 25,000ha of farmland.

Improved navigation for ships and boats

Produces Hydroelectric power for homes, factories and businesses.

Up to 200 million tonnes of soil is being deposited behind the dam every year which reduces the storage capacity of the reservoir

Water in the reservoir is becoming heavily polluted from shipping and waste discharged from cities

Toxic substances from factories, mines and waste tips submerged by the reservoir are being released into the water

1.4 million people were forcibly moved from their homes to accommodate the dam, reservoir and power stations.

Corrupt local officials have taken over $30 million set aside for compensation for those being forced out of their homes

Water Stress and Demand

Key terms:1. Water stress occurs when the

amount of water available does not match the required demand. This may be due to an inadequate supply or may relate to water quality

2. Areas of deficit are locations where the rain that falls does not provide enough water on a permanent basis. Shortages may occur under certain conditions e.g. long periods without rain.

3. Areas of surplus are areas that have more water than is needed – often such areas receive a high rainfall total but have a relatively small population.

Water supply management: Kielder Water Reservoir

Kielder Water is in Northumberland and is the biggest man-made reservoir in northern Europe. It is 12km long and up 52m deep. It cost £167 million to build and was completed in 1982. It was built to meet an expected increase in water demand from north-east England because of the rising population there and the expected growth of the steel and chemical industries. However, these industries haven’t grown as expected, in fact they’ve declined.

Kielder water is a water-transfer scheme – where water is transferred from one area to another. The water is released in the Rivers Tyne, Derwent, Wear and Tees. This helps to maintain river flows when levels are low. Extra water can be released for household and industrial use. Kielder water can provide up to 909 million litres of water a day.

Advantages Disadvantages Kielder Water is a major tourist attraction. This has created

jobs and benefited the local economy The north-east now has the most reliable water supply in

England Only a few families have been moved and re-housed when

the reservoir was built The release of clean water into the Tyne has encouraged

salmon and sea trout to migrate upriver to breed Forest Park, surrounding Kielder Water is harvested for

timber and employs about 200 people If pollution occurs downstream, clean water can be

released to dilute it and flush it out to sea. The water is used to generate renewable HEP at the dam.

One and a half million trees were cut down to build the reservoir